Valve control mechanism for internal combustion engines



May 6, 1958 G. F. w. LENGNICK 2,833,257

VALVE CONTROL MECHANISM FOR NTERNALOOMBUSTION ENGINES Filed July 5, 1955 .Yvenfor GEORSE F- W- LENGAQ'CK United States Patent VALVE CONTROL MECHANISM FOR INTERNAL COMBUSTION ENGINES George F. W. Lengnick, Stuttgart, Germany, assiglor to Daimler-Benz Aktiengesellschaft, Stuttgart-Unterturkheim, Germany Application July 5, 1955, Serial No. 520,020

8 Claims. (Cl. 123-90) The present invention relates to a valve control mechanism for internal combustion engines.

It is the object of the present invention to provide an improved valve control mechanism in which the valve actuation is varied in dependence on the speed of operation of the engine. More specifically, objects of the invention are to increase the valve stroke as the engine is sped up and to reduce same as the engine is slowed down; to vary the timing of the closing of the valve in dependence on the speed of operation of the engine; to close the valve earlier in the cycle of operation at a low speed of the engine and later in the cycle of operation at a higher speed of the engine; to provide simple and reliable means for effecting the aforestated valve control; and to provide an improved valve control mechanism in which both the valve stroke and the timing of the closing of the valve will be varied in dependence on the speed of operation of the engine without varying the timing of the opening of the valve.

Further objects of the present invention will appear from a detailed description of a number of preferred embodiments thereof following hereinafter with reference to the drawings, and the features of novelty will be pointed out in the claims. It is to be clearly understood, however, that such detailed description serves the purpose of illustrating the invention rather than that of restricting or limiting the same. In the drawings,

Fig. l is a sectional elevation of the upper portion of the cylinder head of an internal combustion engine showing part of an inlet valve and part of the linkage for the actuation thereof, the linkage including a hydraulic link forming part of the cam-controlled push rod,

Fig. 2 is a control diagram of the valve actuation,

Fig. 3 is a sectional elevation of the valve control mechanism mounted on the cylinder head of an internal combustion engine showing part of the inlet valve, a cam for controlling the same, and an interposed linkage including a hydraulic link, and

Fig. 4 is a sectional view similar to that of Fig. 3, but on an enlarged scale, of a modification of the hydraulic link shown in Fig. 3.

A cylinder head of an internal combustion engine is provided with an inlet port for air or a gaseous air-fuel mixture and with an outlet port for the exhaust gases, each port being controlled by a poppet valve, the stem 11 of the poppetvalve controlling the inlet port being shown in Fig. l. A cam shaft (not shown) which is geared to the crankshaft of the engine, is provided with a plurality of cams, each cam being adapted to actuate one of the valves. The cam a'cts on a reciprocating member and such member is connected with the associated valve by a linkage to transmit the reciprocatory motion to the valve. The linkage includes a push rod 12 slidably mounted for up-and-down motion and a two-armed lever 13 acting on stem 11 of the valve. The two-armed lever 13 is pivotally mounted on a stud 14 fixed to a bracket 15 secured to the cylinder head 10. One of the arms of lever 13 engages a cap 16 fLxed tothe valve stem 11, and the latter carries a flanged member 17 on which a helical spring 18 acts. The spring 18'is supported on the 2,833,257 Patented May 6, 1958 ice ' opposite direction.

For therpurpose of the present invention the upper end of the cam-actuated push rod 12 is formed integral with a coaxial cylinder 19 in which a piston or plunger 20 is slidably guided. A helical pressure spring 21` inserted between the push rod 12 and the plunger 20 and extending into axial recesses thereof urges the plunger 20 into contact with a cup-shaped member 22 which, in its turn, engages the left arm of lever 13 at the bottom thereof and is slidably guided by its internal cylindrical face on the cylinder 19' and by its external cylindrical face in a flanged guide bushing 23 which is suitably secured to the cylinder head 10 by a plurality of bolts extending through bores of its flange.

The cylinder 19 and the plunger 20 are movable elements and constitute a hydraulic link confining, as they do, a chamber 24 which is filled with a suitable liquid, such as oil.

The variable chamber 24 is connected with a liquid reservoir by each of two ducts. In the embodiment shown, the liquid reservoir is formed by a chamber 25 which surrounds the plunger 20 and is formed by a sleeve 26 of flexible material, such as rubber, which has its lower end sealed against cylinder 19 and its upper end sealed against an external collar provided on plunger 20. One of the ducts which connects the chamber 24 with the reservoir 25 is permanently open and has a restricted cross section. In the embodiment shown in Fig. l this duct is simply formed by the gap 32 provided between the cylinder 19 and the plunger 20, such gap having preferably a width of from about 0.1 millimeters to about 0.2 millimeters. The other duct which connects the chamber 24 with the reservoir 25 is formed by a transverse bore 28 of the plunger and by axial bores 27 and 29 thereof which open into the chamber 24. This duct is controlled by a check valve 30 mounted to open towards the variable chamber 24. The check valve is formed by a ball urged by a helical spring 31 upon a valve seat surrounding the lower end of bore 29.

It is the purpose of the exible sleeve 26 to prevent oil from leaking through between the elements 22 and 19 and from thus getting lost.

The operation of the novel Valve control mechanism is as follows: When the'push rod 12l is lifted in the direction of arrow a by the cam to thereby open the valve contrary to the force exerted by spring 18, the volume of liquid included in the variable chamber 24 transmits the upward motion to the plunger 20 which, in its turn, rocks the lever 13 to thereby depress stem 11 opening the valve. However, a variable part of such motion is absorbed in the hydraulic link, because part of the liquid in the variable chamber 24 will escape through the gap 32 into the reservoir 25 thereby reducing the distance of upward travel of the plunger 20 'with respect to the upward travel of the rod 12. The

absorbed part of the lifting motion a, however, depends on the duration of the period for which the liquid in the variable chamber 24 will be subjected to the pressure of the spring 18. The period, in its turn, however, depends on the speed of operation of the engine. When the engine is running at a very high rate of speed, the liquid hardly finds time to escape from the chamber 24 through the gap 32 when the push rod 12 is lifted so that a very small part only of the upward motion of push rod 12 is absorbed. When the engine is slowed down, however,V a greater quantity of liquid will escape through gap 32 during the valve-opening period and,

140 provided in the cylindrical element 119. An adjustable throttle valve 140 having a threaded stem and a knurled knob engages a threaded lbore provided in the cylindrical element 119 and cooperates with a valve seat 141 provided at the bottom end of the bore 139 to thereby determine the cross section of the communication between the variable chamber 124 and the reservoir 125. In this embodiment, the plunger 120 may have a sealing fit in the cylindrical bore of the element 119. By suitable adjustment of the valve 140 the function of the hydraulic link may be so controlled as to meet the specific requirements of any particular engine. If desired, the plunger 120 may be so fitted in the cylindrical element 119 that a narrow gap 132 is left therebetween which has a smaller cross section than the gap 32 in Fig. l.

From the afore description it will appear that by the means described the lifting stroke of the valve may be controlled without the necessity of providing any control mechanism outside of and in addition to the linkage. While it has been assumed hereinabove that the stem 11, or 111 respectively, is the stem of the inlet valve, it is obvious that the linkage controlling the outlet valve may be likewise provided with a hydraulic link and, more particularly, with a hydraulic link that is leaky and, therefore, absorbs a variable part of the valve-lifting motion.

In the operation of the valve control mechanism movement of the linkage in the valve-opening direction causes the 'hydraulic fluid to be displaced through the restricted duct, such as 32, or 132, or 139, 140, whereby a comparatively small relative displacement of the linkage elements will -be produced when the engine runs at a high rate of speed, and a comparatively large relative displacement of the linkage elements will occur when the engine is operated at a low rate of speed, such relative displacement reducing the valve-opening stroke. The restricted cross section of the duct through which the hydraulic fluid escapes from the variable chamber 24, or 124 respectively, is preferably provided by a loose fit of plunger and cylinder. The provision of the check valve, such as valve 30, or 130 respectively, provided between the variable chamber and the liquid reservoir which `are separated by the restricted cross section, offers the advantage that when the linkage moves in valve-closing direction the elements of the linkage may be easily restored to the initial normal position permitting the liquid that had previously escaped from the variable chamber to quickly return to the same through the check Valve.

The application of the invention to the inlet valve of an internal combustion engine offers the advantage that the gas or air stream entering the cylinder may be given a high speed, even if the engine operates at a low number of revolutions per minute. This is particularly desirable in engines of the type in which the fuel is injected into the cylinder during the suction stroke of the piston and is subsequently ignited by a spark plug.

Moreover, the invention may be used with great advantage in an internal combustion engine in which the periods during which the inlet valve and the outlet valve are open overlap each other. While during operation of the engine at a high speed the valves remain open for a longer period of time thus ensuring a high charge of the cylinder, it is desirable when the engine is operated at a low speed that the opening periods of the valves overlap little or not at all in order to avoid `a loss of the gas charge through the loutlet valve. The novel valve control mechanism complies with that requirement.

Moreover, the novel valve control mechanism ensures a smoother idling and a betterstarting of the engine.

While the invention has been described in connection with a number of preferred embodiments thereof, it will be understood that it is capable of further modification, and this application is intended to cover any variations, uses, or adaptations of the invention following, in general, the principles of the invention and including such departures from the present disclosure as come within known or customary practice in the art to which the invcntion pertains, and as fall within the scope of the invention or the limits of the appended claims.

What l claim is:

l. ln an internal combustion engine, the combination comprising a Valve, a reciprocating linkage connected to said valve, and a rotating cam coordinated to and adapted to impart to said linkage a reciprocatory motion transmitted to said valve, said linkage including means responsive to the rotary speed of said cam and adapted to absorb a variable part of said motion, said speed-responsive means being provided with a passage of definite size forming a hydraulic link, said variable part increasing as said rotary speed decreases, whereby the valve stroke will increase as the engine is sped up and will decrease as the engine is slowed down.

2. In an internal combustion engine, the combination claimed in claim 1 in which said means comprises a cylinder, a piston movable therein, vand a volume of liquid therebetween, a passage of definite cross section being provided in said means permitting said liquid, when said linkage is subjected to pressure, to gradually escape.

3. In an internal combustion engine, the combination claimed in claim 1 in which said means comprises a cylinder, a plunger guided therein,l a volume of liquid filling the space between said cylinder and said plunger, a stop rigidly connected with said cylinder and adapted to limit the outward stroke of said plunger, and a spring tending to urge said plunger out of said' cylinder into contact with said stop, said cylinder being provided with a passage of definite cross section for discharge of said liquid when said linkage is subjected to pressure.

4. In an internal combustion engine, the combination claimed in claim 3 in which said passage of definite cross section is provided between said plunger `and said cylinder.

5. In an internal combustion engine, the combination comprising a valve, a reciprocating linkage connected to said valve, a rotating cam coordinated to and adapted to impart a reciprocatory motion to said linkage, the latter transmitting said motion to said valve, said linkage including relatively movable elements confining a chamber of variable volume, a liquid filling said chamber, and a liquid reservoir, two ducts being provided each connecting said variable chamber to said reservoir, and a check valve adapted to control one of said ducts being mounted to open towards said variable chamber, the other one of said ducts being permanently open and having a restricted cross section.

6. In an internal combustion engine, the combination claimed in claim 5 in which an adjustable throttle valve is coordinated to said other one of said ducts and adapted to adjust said cross section.

7. In an internal combustion engine, the combination claimed in claim 5 in which said relatively movable elements are constituted by a cylinder and a plunger movable therein, said other one of said ducts being formed by a gap of a width of from about 0.1 millimeters to about 0.2 millimeters provided between said cylinder and said plunger.

8. In an internal combustion engine, the combination claimed in claim 5, in which the other one of said ducts enables said liquid to pass back and forth between said chamber and said reservoir.

References Cited in the tile of this patent UNITED STATES PATENTS 2,109,815 Best Mar. 1, 1938 2,158,222 Dayton May 16, 1939 2,178,732 Voorhies Nov. 7, 1939 2,203,952 Eshbaugh June' 11, 1940 2,484,109 Meinecke Oct. 11, 1949 2,547,798 Truxell Apr. 3, 1951 

